package PTA.Pta_ch02;
import java.util.Scanner;
public class ex09 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int a= sc.nextInt();
        double b;
        b=5.0*(a-32)/9;
        System.out.printf("%.2f",b);
    }
}
